JPH04104911A - Recovery of iron oxide - Google Patents

Abstract

PURPOSE:To regenerate the title iron oxide through such processes that when surface-deposited carbon is to be removed from iron oxide particles with oxygen defects disappeared, water or water vapor is brought into contact with the system to produce CO by reaction the oxygen in the iron oxide and the carbon on the surface, resulting in efficient carbon removal. CONSTITUTION:Oxygen defects are forcedly produced in the spinel structure in an iron oxide (magnetite) to effect activation, and using the resultant iron oxide thus activated as a catalyst, the carbon dioxide in automotive exhaust gas, etc., is decomposed to suppress its emission into the air. And, used, deactivated iron oxide particles through the above process, which has been freed from oxygen defects, with carbon powder deposited on the particle surface, are brought into contact with water or water vapor to make reaction between the oxygen in said iron oxide and the carbon on the surface to effect producing carbon monoxide, thus removing the carbon from the surface of said iron oxide. The resultant iron oxide is then activated and reused for carbon dioxide decomposition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering iron oxide by removing carbon deposited on the surface of iron oxide by reaction.

[Prior Art] Iron oxide (magnetite) has been known as a ferromagnetic material and is widely used in various technical fields.

On the other hand, magnetite activated by creating oxygen vacancies in its spinel structure has been found to be extremely useful as a reactive catalyst, allowing new developments in its use in the chemical field.

The inventor previously completed a method of decomposing carbon dioxide gas using activated magnetite (Xiao Guanping 1-30856
(See No. 8). This method, despite the low temperature treatment,
It is an effective technology that can decompose carbon dioxide with nearly 00% decomposition efficiency and can be applied to the removal of carbon dioxide from automobile exhaust gas and exhaust gas from thermal power plants to suppress the release of carbon dioxide into the earth's atmosphere. There are great expectations for its use in the carbon dioxide and oxygen recycling system within the station.

[Problem to be solved by the invention]

By the way, in the above method, first, activated magnetite is produced by reacting Fe, O, and particles with hydrogen, and then CO2 is reacted with this activated magnetite. The reaction formula is shown below.

Magnetite + H2 → activated magnetite + H, 0 activated magnetite + CO3 → C + magnetite In this way, only H2 is used in the first stage, and C sail is reacted in the second stage. Carbon (C)
will precipitate as fine powder on the surface of magnetite particles. Magnetite is an iron oxide, so it is harmless, and there is no possibility of causing any particular pollution problems even if the reacted magnetite is disposed of as is. However, the carbon deposited on the surface is a useful resource, and it is possible to remove it from magnetite. If a technology to separate carbon is established, magnetite can be reactivated into magnetite and carbon can be used as a resource, creating a truly favorable closed cycle.

Especially when considering its use in space stations, recycling magnetite is essential.

An object of the present invention is to solve the above problems and provide a method for easily separating and regenerating carbon from iron oxide through a simple process of simply reacting carbon-containing iron oxide with water or steam. There is a particular thing.

[Means for Solving the Problems] In order to achieve the above object, the method for recovering iron oxide according to the present invention includes a step of reacting water or steam to remove carbon from iron oxide containing carbon. In this method, iron oxide is a particle in which oxygen defects have disappeared, carbon is precipitated on the surface of iron oxide, and the step of reacting with water or steam is , is a process in which carbon-containing iron oxide is brought into contact with water or steam, and carbon monoxide is generated through a reaction between oxygen in the iron oxide and carbon on the surface, thereby removing carbon from the surface of the iron oxide. .

[Principle/effect] Activated iron oxide particles (magnetite particles) used to decompose carbon dioxide lose their activity due to the decomposition reaction,
In principle, it returns to the original iron oxide particles without oxygen defects, but
Carbon powder produced by decomposition of carbon dioxide gas is deposited on its surface. This iron oxide is highly reactive in the carbon precipitate state.

As a result of extensive research into its properties, it was discovered that it generates hydrogen gas and carbon oxide gas when it comes into contact with water or steam. Moreover, it was found that the amount of hydrogen and carbon monoxide generated was determined by the reaction temperature. Although the reaction mechanism is not necessarily clear, structural analysis of iron oxide by X-ray diffraction, measurement of carbon content, iron (It), iron (III)
), it seems that this is due to the following reaction. That is, 1) The reaction occurs at 100°C or higher and generates hydrogen.

The amount of hydrogen generated increases as the reaction temperature rises, reaching approximately 400°C.
becomes the dominant reaction. This reaction occurs when water (H, O,
) is thought to be produced when iron oxide extracts oxygen from the iron oxide. If only inert iron oxide is brought into contact with water or steam under the same conditions, no reaction will occur and no hydrogen will be generated.

U) When the reaction temperature is 550°C or higher, the reaction that generates -carbon oxide becomes dominant. It is clear that this reaction occurs because the oxygen in the iron oxide oxidizes the carbon on the surface due to the high temperature.

The reactions i) and ii) above are due to the direct precipitation of very fine carbon powder on the surface of iron oxide (magnetite) particles.

Therefore, if water or steam is reacted with carbon-containing iron oxide mainly under temperature conditions of 550°C or higher,
Carbon and iron oxide can be effectively separated. The resulting carbon-free pure iron oxide can be reactivated and recycled for carbon dioxide decomposition treatment, and the carbon can be recovered as a useful resource energy gas.

The above describes the recovery of iron oxide (magnetite) used in the decomposition treatment of carbon dioxide gas, but the reaction that ultimately produces iron oxide containing carbon is not limited to this. The present invention can be similarly applied to other reactions as long as carbon is similarly precipitated and is included in magnetite.

Note that in addition to magnetite and ferrite, wustite and the like can be used as the iron oxide.

[Effects of the Invention] As described above, according to the present invention, carbon can be effectively removed from carbon-containing iron oxide produced as a reaction product to extract pure iron oxide. By applying the present invention to the technology of using magnetite to decompose carbon dioxide gas, it is possible to realize a simple and useful gas separation system that can be used in outer space, and a system for recycling oxygen and carbon dioxide.

[Example] Examples of the present invention are shown below.

Magnetite (FeO0.) was packed in a lOg quartz column, and hydrogen gas was passed at 300'C for 4 hours to obtain oxygen-deficient iron oxide. Next, carbon dioxide was introduced into the column and reacted at 3°0°C to precipitate carbon on the magnetite surface. This iron oxide contained 4% carbon. next,
Fill a quartz cell with 5 g of iron oxide with carbon attached, and
0℃, 2506C, 350℃, 450℃, 550℃, 6
Steam heated to various temperatures of 50°C was brought into contact with iron oxide, and changes in the resulting gas were investigated. Table 1 shows the component composition of the reaction gas at each temperature. As is clear from Table 1,
It can be seen that when the reaction temperature is 450° C., the amount of hydrogen gas generated increases, but as the reaction temperature increases thereafter, the amount of hydrogen gas generated decreases, and conversely, the amount of CO gas generated increases. Therefore, by selecting the reaction temperature to be 550° C. or higher, carbon can be separated from magnetite in a short time.

Table 1

Claims (1)

[Claims] (1) A method for recovering iron oxide by removing carbon from carbon-containing iron oxide, which involves a step of reacting water or steam, and ferrous oxides are particles in which oxygen defects have disappeared. and carbon is
It is precipitated on the surface of iron oxide, and the step of reacting with water or steam is to bring water or steam into contact with iron oxide containing carbon, and the oxygen in the iron oxide reacts with the carbon on the surface. 1. A method for recovering iron oxide, which is a step of generating carbon monoxide and removing carbon from the surface of iron oxide.